Selective Grain Size Fractionation, CO2-Enhanced Aqueous Extraction and Characterization of Trona, a Non-marine Evaporite Mineral, Originating from Semi-arid Soil Sediments

Abstract

Beneficiation of white-powdery mineral, from selective grain size (63 – 200 µm) sand fractions and its characterization as trona, a non-marine evaporite, exudates as efflorescent crust, originated from the semi-arid region soil sediments, occurring at Siddhamalli, Tamil Nadu, India is described, by a five-stage process. Aqueous extraction of selective sand fractions, in CO2-enhanced medium, resulted in white crystalline powder, is chemically characterized as sodium sesquicarbonate dihydrate, [Na3H(CO3)2.2H2O]. The % yield of trona is directly proportional to the % fine and very fine sand fractions and inversely proportional to the % coarse fractions (0.5 – 1.0 mm), as revealed by grain-size analysis. CO2-enhanced medium significantly increases the yield, additionally by 20 %.PXRD data revealed the presence of trona with traces of nahcolite and natrite phases. FT-Raman spectrum revealed the characteristic bands correspond to carbonate group. The hydroxyl stretching of water is observed at 3400 cm-1 inferred from FT-IR spectral studies.The content of sodium and trace elements analysed by ICP-OES and water of hydration by TGA, are found to be good agreement with the calculated values of Na (30.58 %) and dihydrate (15.97 %) respectively. SEM images revealed the less agglomerated particles of sizes ranging from 0.093 - 0.44 µM. Geologically, soil sediments fall in tractive current, from talus of Bouldery sandstone and shale of Talchir formation, Lower Gondwana of Upper Carboniferous to Lower Permian Age. Trona is popularly known as “Po¯neeru” in Indian traditional Siddha system of medicine finds its application in most of the drug formulations.